The present invention relates generally to voltage regulators, and, more particularly, to a digitally-assisted voltage regulator with performance compensation.
Integrated circuits such as system-on-chips (SoCs) and application specific integrated circuits (ASICs) often are designed as mixed signal circuits, which integrate various components such as amplifiers, analog-to-digital converters, digital-to-analog converters, step-up converters, and boost converters (hereinafter “electronic components”) on a single chip. A boost converter steps-up a supply voltage and provides the stepped-up voltage to other electronic components. Boost converters are susceptible to variations in physical operating conditions such as process, voltage, and temperature (PVT). For example, process spread during manufacturing may affect operational parameters such as bandwidth, slew rate, and leakage current of the electronic components. An unstable supply voltage and heating of the boost converter may result in voltage and temperature variations. Thus, PVT variations may degrade the performance of the boost converter, which in turn affects the performance of other mixed signal circuits driven by the boost converter.
A boost converter includes an on-chip voltage regulator to compensate for voltage variations. The voltage regulator rejects noise injected into the supply voltage from a voltage source to provide a stable supply voltage. However, the process and temperature variations can still effect the regulated supply voltage. One solution to overcome this problem is to connect on-chip process and temperature sensors to the voltage regulator to compensate for PVT variations.
FIG. 1 is a schematic block diagram of a conventional boost converter 100. The boost converter 100 includes process and temperature sensors 102 and 104 connected to a voltage regulator 106. The boost converter 100 further includes a gate driver 108, a transistor 110, an inductor 112, a diode 114, a load capacitor 116, a load 118, and a voltage supply 120. The process and temperature sensors 102 and 104, the voltage regulator 106, the gate driver 108, and the transistor 110 typically are integrated on an integrated circuit (IC) 122, while the inductor 112, diode 114, load capacitor 116, load 118, and voltage supply 120 typically are off-chip.
The voltage supply 120 provides a supply voltage VSUPPLY. The process sensor 102 is connected between the voltage supply 120 and ground, and generates a process compensation signal PCS. The temperature sensor 104 also is connected between the voltage supply 120 and ground, and generates a temperature compensation signal TCS. The voltage regulator 106, which also is connected between the voltage supply 120 and ground, receives the process and temperature compensation signals PCS and TCS, and generates an output voltage VOUT. The gate driver 108 is connected between the voltage regulator 106 and ground, and receives the output voltage VOUT from the voltage regulator 106, a control signal ENABLE from an external control circuit (not shown), and generates a gate driver signal GDS.
The transistor 110 has a gate connected to the gate driver 108 for receiving the gate driver signal GDS, a source connected to ground, and a drain connected to a node between the inductor 112 and the diode 114. When the gate driver signal GDS is active, it switches ON the transistor 110. The diode 114, which is connected between the inductor 112 and the load capacitor 116, prevents the load capacitor 116 from discharging back to the transistor 110. The load capacitor 116, which is connected between the diode 114 and ground, supplies a load current to the load 118 when the transistor 110 is ON.
When the transistor 110 is switched ON, the diode 114 is reverse biased, and the inductor 112 is connected to the voltage supply 120 by way of the transistor 110. As the supply voltage VSUPPLY has a constant voltage level, the inductor 112 is charged by a linearly increasing current of the supply voltage VSUPPLY. The load 118 discharges the load capacitor 116. Conversely, when the transistor 110 is switched OFF, the diode 114 is forward biased, and the inductor 112 is connected to the load capacitor 116 by way of the diode 114. The inductor 112 then charges the load capacitor 116.
Process and temperature variations affect the operational parameters of the gate driver 108, which in turn causes the ramp-rate of the gate driver signal GDS to deviate from a desired ramp-rate. The ramp-rate represents the rate of increase of current in the gate driver signal GDS. The deviation of the GDS ramp-rate results in erroneous switching of the transistor 110. The process and temperature sensors 102 and 104 measure process and temperature variations, and generate the process and temperature compensation signals PCS and TCS, respectively, which the voltage regulator 106 uses to generate the output voltage VOUT.
Although the process and temperature sensors 102 and 104 compensate for process and temperature variations, they increase die area, making the boost converter 100 bulky and complex, and increasing the cost of the IC 122. Therefore, it would be advantageous to have a boost converter that compensates for PVT variations but does not require process and temperature sensors.